1. Field of the Invention
The present invention relates to apparatus for processing raw foods for packaging, and particularly to methods and apparatus for killing surface microorganisms and treating the surface layer of foods such as meats, seafood, grains, fruits and vegetables. For purposes of this application, the apparatus may be referred to as a surface pasteurizer, although treatment of the surface layer may be primarily for purposes other than sterilization.
2. Description of the Related Art
Various methods and apparatus have been developed in recent years for sterilizing or otherwise treating raw foods, some of which employ treatment with liquids others with gases, some at high pressure, others at atmospheric pressure, and still others under vacuum.
German Patent No. 2,422,907, published Nov. 20, 1975, discloses a method and apparatus for sterilizing bulk goods (flour, cocoa, filler material for cosmetics and pharmaceuticals, etc.) using superheated steam, holding the goods at rest in an after sterilization zone at the sterilization temperature. European Patent 269,257, published Jan. 22, 1992, shows a method for sterilizing herbs and spices by exposure to steam at 5-50 psi for 10 seconds to 5 minutes, followed by insertion into a second vessel under vacuum, chilling by a water cooled jacket, and increasing to atmospheric pressure by adding nitrogen. European Patent 271,915, published May 20, 1992 shows an apparatus and method of sterilizing root and tuber vegetables in slices or pieces less than 7 mm by steam treatment under pressure.
U.S. Pat. No. 5,213,029, issued to Hideki Yutaka May 25, 1993, discloses an apparatus for treating foods under high pressure applied by a liquid pressure medium. U.S. Pat. No. 5,268,185, issued Dec. 7, 1993 to Bender, et al., teaches treatment of red meat with a solution of alkali metal organophosphates to remove bacterial contamination. U.S. Pat. No. 5,344,609, issued Sep. 6, 1994 to Marshall Long, shows a method and apparatus of treating sliced and chunked foods by steam under pressure, reducing pressure in successive stages to emit steam until room temperature is reached. U.S. Pat. No. 5,368,872, issued Nov. 29, 1994 to Don M. Davis, Jr. shows an apparatus for smoking meats under pressure and under vacuum, where pressure, temperature and smoke concentration are controlled.
U.S. Pat. No. 5,403,602, issued Apr. 4, 1995 to Felix W. Endico, teaches treatment of viscous (tuna salad, egg salad, shrimp salad) and semi-viscous (catsup, pickle relish, sauces and salad dressings) food products with ozone in a mixer or blender. U.S. Pat. No. 5,433,142, issued Jul. 18, 1995 to Eldon Roth discloses using a working gas, such as CO.sub.2, N.sub.2, O.sub.2, or H.sub.2 under pressure from 10 psig to 4,000-5,000 psig. U.S. Pat. No. 5,439,694, issued Aug. 8, 1995 to William F. Morris, Jr., shows processing poultry in a steam chamber after evisceration and before chilling long enough to kill salmonella. U.S. Pat. No. 5,458,901, issued Oct. 17, 1995 to Engler, et al., teaches introducing meat to a pressure vessel, removing air to create a vacuum, introducing CO.sub.2 at 350-400 psig and 32-36.degree. F. for 15 minutes to form carbonic acid, and rapidly depressurizing the vessel.
U.S. Pat. No. 5,460,845, issued Oct. 24, 1995 to Delmassa, et al., shows treating the surface of seeds, nuts, grains, fruits and spices in a dehumidifying chamber, exposing the food to H.sub.2 O.sub.2 and H.sub.2 O vapor under vacuum, followed by removing the peroxide to 38 mm Hg, followed by increasing the pressure to 400-580 mm Hg, for a 3-30 minute exposure. U.S. Pat. No. 5,514,403, issued May 7, 1996 to Webb, et al., teaches killing bacteria on animal carcasses by spraying with superheated steam at 250-300.degree. F. for 1-5 seconds followed immediately by spraying with a cooling liquid for 5-10 seconds. U.S. Pat. No. 5,523,053, issued Jun. 4, 1996 to Daniel H. Dudek, describes sterilizing spices or herbs by dropping the material into pressurized steam sterilization chambers successively for a predetermined period of time, followed by gradual depressurization to atmospheric pressure.
U.S. Pat. No. 5,593,714, issued Jan. 14, 1997 to Gerald P. Hirsch, describes placing a food product in a compressible package at 25,000 psi and 18-23.degree. C. at least 5 days, optionally adding an anti-oxidant. U.S. Pat. No. 5,641,530, issued Jun. 24, 1997 to T. C. Chen, teaches treating foodstuffs with 0.005% to 0.035% H.sub.2 O.sub.2 and 0.005 to 0.1% H.sub.3 PO.sub.4 or C.sub.6 H.sub.5 COOH. U.S. Pat. No. 5,711,981, issued Jan. 27, 1998 to Wilson, et al., describes treating meats by removing surface water by air blowing, steam heating at pressure greater than atmospheric, and chilling by spraying with water.
All of these techniques have suffered from one or more of the following problems: (1) denaturation of meat protein, (2) insufficient bacterial kill, (3) deleterious color change, (4) unacceptable flavor modification, and (5) inadequate control of the process in large scale operations.
A previous patent to the present inventor, Arthur I. Morgan, U.S. Pat. No. 5,281,428, issued Jan. 25, 1994, described a method and apparatus for killing microorganisms on the surface of raw meat, the method comprising the steps of (1) exposing the meat to a vacuum; (2) flushing the surface with an air-free treatment gas; (3) treating the meat surface with air-free treatment gas; and (4) reexposing the meat to a vacuum. While the method and apparatus described therein are effective in accomplishing the object of killing surface microorganisms without substantial change in the interior of the meat product, nevertheless, in practice the method and apparatus require significant and unobvious modifications and adaptations to produce a practical and economical apparatus serviceable in the industry.
For example, the method as set forth in '428 called for exposing the raw meat to a vacuum and then flushing the surface of the meat with an air-free gas prior to treatment in order to further remove air from the pores, close to the surface of the meat so that the treatment gas is more quickly enabled to stream over the surface of the meat to kill microorganisms, thus reducing the exposure time to the treatment gas and reducing the likelihood of cooking or changing the interior of the meat. As set forth more fully below, applying the vacuum prior to flushing requires the vacuum pump to remove air from the treatment chamber at a prodigious rate, engendering frequent mechanical breakdowns, or slowing the treatment process, which makes the apparatus less economical and less desirable from an industrial perspective. It is an object of the present invention to overcome the difficulties and disadvantages of the prior art.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus a apparatus for treating raw food solving the aforementioned problems is desired.